208 Version Final rev2 laude (51635)
This print-out should have 60 questions.
Multiple-choice questions may continue on
the next column or page nd all choices
before answering.
001 5.0 points
Consider the irreversible reaction
1
3. I, II, III
4. III only
5. II only
6. I, II
Which of the following correctly expresses
the rate of change of [B] ?
[B]
1
= (rate of rxn)
t
2
[B]
2.
= +(rate of rxn)
t
1
[B]
= + (rate of rxn)
3.
t
2
[B]
4.
= (rate of rxn)
t
[B]
= 2 (rate of rxn) correct
5.
t
[B]
6.
= +2 (rate of rxn)
t
Explanation:
As B is a reactant and consequently disappears during the reaction, its rate of change
will be negative and the inverse of the coecient is used when writing the rate:
1.
1 [B]
2 t
[B]
2 (rate of rxn) =
t
(rate of rxn) =
002
5.0 points
Which of the following statements is/are
always true concerning Kw ?
I) It gets larger as the temperature increases
II) It equals 1014
III) Kw = [H+ ][OH ]
7. I, III correct
Explanation:
All equilibrium processes are temperature
dependent, and because auto-protolysis is endothermic, Kw increases as temperature increase. Thus statement I is true, but statement II is only true at room temperature.
Statement III is the denition of Kw .
003 5.0 points
Consider the potential energy diagram shown
below.
Energy (kJ)
A + 2B 3C.
350
B
300
250
A
Reaction progress
What is the activation energy Ea for the
reaction A B?
1. 350 kJ
2. 250 kJ
3. 150 kJ
4. 100 kJ correct
5. 50 kJ
1. I only
Explanation:
We need enough energy to get to the top of
the hill in order to fall down to the products.
So the energy must raise from 250 kJ (at A)
up to the top of the hill at 350 kJ:
2. II, III
350 kJ 250 kJ = 100 kJ
Version 208 Final rev2 laude (51635)
2
Explanation:
004
5.0 points
Which of the following pairs of solutions
would result in a buer upon mixing?
1. 1 L of 0.5 M CH3 NH2 ; 1 L of 0.5 M HF
2. 1 L of 2 M (CH3 )2 NH2 Cl; 1 L of 1 M
HCl
3. 2 L of 0.5 M NaHCOO; 1 L of 1 M LiOH
1
1
= akt
[A]t
[A]0
1
1
=
+ akt
[A]t
[A]0
1
+
=
0.400
(0.103 M1 min1 ) (60 min)
= 8.68
[A]t = 0.115 M
4. 0.25 L of 1 M H2 SO3 ; 0.5 L of 1 M NH3
5. 0.5 L of 1 M Ca(OH)2 ; 2 L of 1 M
CH3 COOH correct
Explanation:
A buer prepared by a neutralization reaction requires either a weak acid and less
strong base or a weak base and less strong
acid. The only pair of substances that is usable is the strong base Ca(OH)2 and the weak
acid CH3 COOH.
005 5.0 points
Consider the following reaction and its rate
constant.
AB
k = 0.103 M 1 min1
What will be the concentration of A after
1 hour if the reaction started with a concentration of 0.400 M ?
1. 0.115 M correct
006 5.0 points
A fatty acid consists of a ten-carbon alkane
with a carboxylic acid functional group.
What would you propose as the name for
this fatty acid?
1. dodecanoic acid
2. decanoic acid correct
3. dodecanoate acid
4. dodecanol
5. decanecarboxylate
Explanation:
The prex for 10 carbons in a chain is deca.
007 5.0 points
For a reaction in acid involving the following
two half reactions,
Fe3+ + e
2. 0.384 M
3. 0.308 M
4. 0.236 M
Cr2 O2 + 6 e
7
Fe2+
2 Cr3+
what is the coecient for H+ in the balanced
reaction?
5. 0.152 M
1. 7
6. 8.28 104 M
2. 36
7. 0.0843 M
3. 14 correct
8. 0.361 M
4. 1
Version 208 Final rev2 laude (51635)
3
Cu Cu2+ 2e- -.34 V
That gives an overall potential of +.18 V
5. 6
Explanation:
The balanced equation is
14 H+ + 6 Fe3+ + Cr2 O7
6 Fe2+ + 2 Cr3+ + 7 H2 O
008 5.0 points
If a battery is dropped into a beaker of salt
water (NaCl solution), which gas is formed at
the cathode of the resulting electrolytic cell?
1. H2 correct
010 5.0 points
Catalytic converters are installed in automobiles to speed up which two of the following
reactions?
I) CO CO2
II) CO2 CO
III) NO2 N2
IV) N2 NO
V) O2 O3
VI) O3 O2
2. Na
1. I and III correct
3. Cl
2. II and III
4. O2
3. I and VI
5. H
4. V and VI
6. Cl2
5. I and IV
Explanation:
009 5.0 points
Consider the reaction
2 Cu+ (aq) Cu(s) + Cu2+ (aq) .
If the standard potentials of the Cu2+ |Cu
and Cu+ |Cu couples are +0.34 and +0.52 V,
respectively, calculate the value of E for the
given reaction.
1. + 0.86 V
2. + 0.18 V correct
6. II and IV
Explanation:
Catalytic converters convert products of incomplete combustion such as unburnt hydrocarbons and CO into CO2 and H2 O. They
also convert various oxides of nitrogen formed
in the high temperature environment of the
combustion back into N2 gas.
011 5.0 points
The vapor pressure of pure water (H2 O) at
30 o C is 40 torr. If salt (NaCl) is dissolved
into a sample of water until the total vapor
pressure of the mixture at 30 o C is 32 torr,
what is the mol fraction of salt?
3. 0.18 V
1. 0.65
4. + 0.70 V
2. 0.5
5. 0.70 V
3. 0.2 correct
Explanation:
combine the 1/2 reactions in the following
ways...
2 Cu+ + 2e- 2Cu +.52 V
4. 0.35
5. 0.8
Version 208 Final rev2 laude (51635)
Explanation:
P = Po
water water
P
water = o
Pwater
32
water =
= 0. 8
40
salt = 1 water = 1 0.8 = 0.2
4
3. uorine has a high electronegativity.
4. uorine is a strong oxidant.
5. uorine gas is very reactive.
012 5.0 points
How much heat is required to vaporize 50.0
g of water if the initial temperature of the
water is 25.0C and the water is heated to
its boiling point where it is converted to
steam? The specic heat capacity of water
is 4.18 J ( C)1 g1 and the standard enthalpy of vaporization of water at its boiling
point is 40.7 kJ mol1 .
Explanation:
014 5.0 points
Which of the following metals is not commonly used to prevent the corrosion of steel?
1. Y
2. Na correct
3. Mg
1. 169 kJ
4. Zn
2. 129 kJ correct
Explanation:
3. 40.7 kJ
015
4. 23.5 kJ
5.0 points
5. 64.2 kJ
Explanation:
m = 50 g
Tf = 100 C
Hvap = 40.7 kJ/mol
Ti = 25 C
C = 4.18 J/g/ C
50 g
(40.7 kJ/mol)
18 g/mol
= 128.731 kJ
B
pH
m
Hvap
H = m C T +
MM
= (50 g) (4.18 J/g/ C)
(100 25) C
C
A
1 kJ
1000 J
+
013 5.0 points
The lattice enthalpies of ionic compounds of
uoride tend to be very high because
1. the uoride ion has an oxidation state of
1.
2. the uoride ion is small. correct
Volume
On the titration curve above, at which of
the following points does the acid/base calculation used to approximate the pH not require
an equilibrium constant?
1. A and C
2. A, B and C
Version 208 Final rev2 laude (51635)
3. A and B
4. A
5. C correct
6. B and C
7. B
Explanation:
Before the equivalence point, the Ka is relevant (point A). At the equivalence point, the
Kb of the conjugate base is relevant (point
B). Beyond the equivalence point, the solution consists of a strong base and the pH is
not calculated using any equilibrium constant
(point C).
016 5.0 points
A 100 mL portion of 0.3 M acetic acid is being titrated with 0.2 M NaOH solution. What
is the pH of the solution after 100 mL of the
NaOH solution has been added? The ionization constant of acetic acid is 1.8 105 .
CH3 COOH CH3 COO + H+
0.01 mol
0.02 mol
0. 2 L
0. 2 L
0.05 M
0. 1 M
x
Thus
CH3 COO H+
Ka =
[CH3 COOH]
0. 1 x
1.8 105 =
0.05
Ka [CH3 COOH]
x = H+ =
[CH3 COO ]
1.8 105 (0.05)
=
0. 1
= 9 106
Thus
2. pH = 5.05 correct
017 5.0 points
The graph is a plot of ln A vs t for the reaction
AB
1.2
1.0
0.8
0.4
0.2
3. pH = 6.06
1
4. pH = 4.53
2
3
4
5
rate = k [A] is the rate law for this reaction.
What was the initial concentration of [A]?
5. pH = 4.03
Explanation:
VCH3 COOH = 100 mL [CH3 COOH] = 0.3 M
VNaOH = 100 mL
[NaOH] = 0.2 M
5
Ka = 1.8 10
For CH3 COOH, (0.3 M)(0.1 L) = 0.03 mol
For NaOH, (0.2 M)(0.1 L) = 0.02 mol
0.03 mol
0.02 mol
0.01 mol
pH = log H+ = 5.05
0.6
1. pH = 5.57
CH3 COOH +
5
NaOH
NaCH3 COO
+ H2 O
0.02 mol
0 mol
0.02 mol
+0.02 mol
0 mol
0.02 mol
1. 1.1 M
2. 3.0 M correct
3. 1.8 M
4. 5 M
5. 0.6 M
Explanation:
018 5.0 points
A portion of the polymer Orlon is
Version 208 Final rev2 laude (51635)
CH
CN
CH
CH
H
CH
CN
H
CH2
2. a condensation; H2 C
CN
CH2
CH2
4. a condensation; H3 C
5. an addition; H2 C
CN
CH
3. a rearrangement; H3 C
CH
CN
CN
CN correct
5.0 points
Voltmeter
1.56 V
e
Ag+ cations are attracted to the solid Ag
electrode where they are reduced to Ag(s).
020 5.0 points
Which one of the following is a covalent hydride?
1. RbH
2. NaH
3. SrH2
4. PH3 correct
Explanation:
019
cell the reduction half reaction is
Ag+ (g) + e Ag(s) .
polymer made from the
This is
?
monomer ? .
1. an addition; H3 C
6
e
V
Zinc
(Anode)
Silver
(Cathode)
Explanation:
Hydrogen forms covalent compounds with
nonmetals and ionic compounds with metals.
021
5.0 points
Which of the following equations does not
require any assumptions in order to provide
an accurate solution?
Salt
bridge
to carry
ions
1 M Ag+ (aq)
1 M Zn2+ (aq)
5. CaH2
In this electrochemical cell, what is the reduction half reaction?
1. [OH ] = Kb
Cb
Ca
2. all require assumptions correct
1. Zn(s) Zn2+ (aq) + 2 e
3. [OH ] = (Kb Cb )1/2
2. Zn2+ (aq) + 2 e Zn(s)
4. [H+ ] = Ca
3. Ag+ (g) + e Ag(s) correct
5. [H+ ] = (Ka Ca )1/2
Explanation:
All of these equation assume, at the very
least, that autoprotolysis is negligible.
4. Ag(s) Ag+ (g) + e
Explanation:
+
2+
Zn(s) + 2 Ag (aq) Zn
(aq) + 2 Ag(s)
Reduction occurs at the cathode. In this
022 5.0 points
Kc = 2.6 108 at 825 K for the reaction
2 H2(g) + S2 (g)
2 H2S(g)
Version 208 Final rev2 laude (51635)
The equilibrium concentration of H2 is 0.0020
M and that of S2 is 0.0010 M. What is the
equilibrium concentration of H2 S?
1. K =
3. K =
3. 1.02 M correct
4. 0.0010 M
PF e
PO2 PF e2O3
4. K =
Explanation:
Kc = 2.6 108
[S2 ]eq = 0.0010 M
PO2 3/2 PF e2 O3
Explanation:
Set up K , products in the numerator, reactants in the denominator, all raised to respective stoichiometric coecients.
2 H2 S
[H2 S]2
[H2 ]2 [S2 ]
Kc [H2 ]2 [S2 ]
(2.6 108 ) (0.0020 M)2 (0.0010 M)
= 1. 0 M
023
2
PF e
[H2]eq = 0.0020 M
2 H2(g) + S2
=
correct
1
PO2
2. 10 M
[H2 S] =
3/2
PO2
2. K =
1. 0.10 M
Kc =
1
025 5.0 points
0.5 M of HCOOH is dissolved in water. Which
equation describes a possible mass balance
equation for this system?
1. CHCOOH = [HCOOH]
5.0 points
The functional group
O
2. CHCOOH = [HCOO ]
is called
RCOR
3. CHCOOH
= [HCOOH] + [HCOO ] + [H+ ]
4. CHCOOH = [HCOOH] + [HCOO ] correct
1. an amide.
2. an alcohol.
5. CHCOOH = [HCOO ] + [H+ ]
3. an ester. correct
4. a carboxylic acid.
5. an ether.
Explanation:
RCOOR represents an ester.
Explanation:
026 5.0 points
Which of the following phase changes is not
correctly paired with the sign of its change in
enthalpy?
1. melting, H is +
024
7
5.0 points
2. deposition, H is + correct
Write the equilibrium expression for the
following reaction:
3
2 F e(s) + O2 (g ) Fe2 O3 (s)
2
3. condensation, H is 4. freezing, H is -
Version 208 Final rev2 laude (51635)
8
2.3 103 exp
5. vaporization, H is +
Explanation:
Deposition is an exothermic phase change
and H is negative.
027 5.0 points
Blood, sweat, and tears are about 0.15 M
in sodium chloride. Estimate the osmotic
pressure of these solutions at 37 C. The gas
constant is 0.0821 L atmmol1 K1 .
1. 11 atm
Explanation:
k2
Ea
ln
=
k1
R
029
1, 200
8.314
1
1
298 273
1
1
T1 T2
5.0 points
Consider the equations
Ag+ (aq) + e Ag(s)
E = 0.80 V
Fe3+ (aq) + e Fe2+ (aq)
E = 0.77 V
Cu2+ (aq) + 2 e Cu(s)
E = 0.34 V
Which is the strongest reducing agent?
2. 0.91 atm
1. Fe2+
3. 7.6 atm correct
2. Cu2+
4. 1.8 atm
3. Cu correct
5. 3.8 atm
4. Ag+
Explanation:
028
5. Ag
5.0 points
If a certain reaction has an activation energy (Ea ) of 1.2 kJ mol1 , and a rate constant (k ) of 2.3 103 s1 at a room temperature, which expression could be used to solve
for its rate at 273 K ? Note: exp(x) is another
way of writing ex
1. k2 =
2.3 103 exp
2. k2 =
2.3 103 exp
correct
3. k2 =
2.3 103 exp
4. k2 =
3
2.3 10 exp
5. k2 =
1. 2
8.314
1, 200
8.314
1
1
273 298
1
1
298 273
1, 200
8.314
1
1
273 298
1. 2
8.314
1
1
298 273
Explanation:
The strongest reducing agent must produce
e the best. That is an oxidation reaction
and Cu2+ (aq) + 2 e Cu(s) has the most
positive value (0.34 V vs 0.77 V and 0.80
V).
The ions listed (Ag+ , Cu2+ , Fe2+ ) cannot reduce something else because they would
have to donate e and go to even higher oxidation states. Only the metals are candidates.
030 5.0 points
Rank following salts from least to most soluble:
AgI
Ksp = 1.5 1016
Ag2 CO3
Ksp = 6.2 1012
Ag2 S
Ksp = 1.6 1049
AgSCN
Ksp = 1.2 1012
1. Ag2 CO3 lt; Ag2Slt; AgIlt; AgSCN
2. AgI < AgSCN < Ag2 CO3 < Ag2 S
3. AgSCN < Ag2 CO3 < Ag2 S < AgI
Version 208 Final rev2 laude (51635)
4. Ag2 Slt; AgIlt; AgSCNlt; Ag2CO3
rect
cor-
Explanation:
Molar solubility can be approximated by
taking the nth root of the Ksp where n
is the number of ions in the salt. Doing so results in approximate molar solubilities of 108 , 104 , 1016 and 106 M for
silver iodide, silver carbonate, silver sulde
and silver thiocyanate, respectively. Arranging from least to most soluble produces:
Ag2 S < AgI < AgSCN < AgC O3
031 5.0 points
The reaction for the synthesis of ammonia
N2 (g) + 3 H2 (g)
2 NH3 (g)
is exothermic. To obtain the greatest yield of
NH3 , this reaction should be carried out at
1. any temperature, any pressure.
2. high temperature, low pressure.
3. high temperature, high pressure.
4. low temperature, high pressure. correct
5. low temperature, low pressure.
Explanation:
The reaction is exothermic, so heat is produced. Consider the heat given o by the
exothermicity to be a product of reaction. the According to Le Chatliers Principle,
the reaction will proceed to relieve the stress
applied to the system, so a low temperature
will result in the forward reaction being favored. This produces heat to relieve the stress
of the low temperature. Regarding the pressure, n = 2, so fewer product molecules
are present than reactant molecules. High
pressure will cause the forward reaction to be
favored since this will relieve the pressure.
032 5.0 points
The alkali metals all react with water. Which
is the MOST reactive metal?
9
1. K
2. Li
3. Rb
4. Cs correct
5. Na
Explanation:
033 5.0 points
What metal (in various oxidation states) is
present at both the cathode and the anode in
a typical car battery?
1. cadmium
2. zinc
3. iron
4. nickel
5. copper
6. lead correct
Explanation:
A car battery is also known as a lead storage
battery.
034 5.0 points
For a solution labeled 0.10 M H3 PO4 (aq),
1. [H+ ] = 0.30 M.
2. [H+ ] = 0.10 M.
3. [PO3 ] = 0.10 M.
4
4. [H+ ] is less than 0.10 M. correct
5. [H2 PO ] is greater than 0.10 M.
4
Explanation:
035 5.0 points
Consider the mechanism
NO2 + F2 NO2 F + F
k1 , slow
F + NO2 NO2 F
k2 , fast
What is the rate law?
1. rate = k2 [NO2 ] [F]
2. rate = k1 [NO2 ] [F2] correct
3. rate = k2 [NO2 ]2
4. rate = k1 k2 [NO2 ]2
5. rate = k1 [NO2 F] [F]
Explanation:
036 5.0 points
Many foods will last longer if they are refrigerated. Which of the following BEST explains
why this reduction in temperature helps in
food storage?
Molar Gibbs energy, Gm
Version 208 Final rev2 laude (51635)
10
pure liquid
solid
solvent
Temperature, T
Referring to the graph above, and using
your knowledge of Hsolution , complete the
following statement concerning freezing point
depression:
The molar (enthalpy/entropy) of a pure
liquid is always (greater/less) than that of
a dilute solution. This lowers the value of
Gm for the solvent at all temperatures, thus
lowering the freezing point.
1. enthalpy; greater
1. The reactions occuring must be exothermic and cooling causes fewer decomposition
products to be formed.
2. entropy; less correct
2. Decomposition has nothing to do with
chemistry and is best left to biologists.
4. entropy; greater
3. Solution viscosity increases with lower
temperature and slows the reaction.
4. The kinetics for the enzymatic processes
of microorganisms responsible for decomposition are slowed. correct
Explanation:
At lower temperatures the biochemical reactions occur more slowly.
037
5.0 points
3. enthalpy; less
Explanation:
G = H T S , so in order to decrease G at a
given temperature, we have to either decrease
H or increase S . We know the Hsolution can
be positive or negative depending on the solute, but colligative properties dont depend
on the identity of the solute, so the eect on
the enthalpy is not a good explanation. We
also know that mixtures always have more entropy than pure substances, so that must be
the best explanation.
038 5.0 points
Which one of the following four is not included
in the Arrhenius equation?
1. absolute temperature
Version 208 Final rev2 laude (51635)
2. mass of the catalyst correct
3. activation energy
4. specic rate constant
Explanation:
k = A eEa /(R T ) ,
which includes terms for a specic rate constant, activation energy, and absolute temperature. The catalyst provides an alternate
reaction path with a lower activation energy.
11
041 (part 1 of 2) 5.0 points
The solubility product constant for BaF2 at
25 C is Ksp = 1.7 106 . Calculate the molar solubility of barium uoride (BaF2 ) in
water at 25 C.
1. 7.5 103 mol/L correct
2. 9.2 104 mol/L
3. 1.3 103 mol/L
4. 1.2 102 mol/L
Explanation:
039 5.0 points
What is the pH of a solution containing 109
M HClO4 ?
1. 8.768
042 (part 2 of 2) 5.0 points
What is the molar solubility of barium uoride (BaF2 ) in 0.15 M NaF at 25 C?
1. 5.7 106 mol/L
2. 5.000
2. 7.6 105 mol/L correct
3. 6.996 correct
3. 1.1 105 mol/L
4. 9.000
4. 1.9 105 mol/L
5. 5.232
Explanation:
Explanation:
040 5.0 points
These acids are listed in order of decreasing
acid strength: HCl, H3 O+ , HCN. List their
conjugate bases in order of decreasing base
strength (strongest base to weakest base).
043 5.0 points
600 mL of a 0.6 M solution of HClO is titrated
with a solution of 0.9 M NaOH. What is the
pH after adding 400 mL of the NaOH solution? The ionization constant for HClO is
3.6 108 .
1. OH , CN , Cl
1. 9.5
2. Cl , OH , CN
2. 4.5
3. Cl , H2 O, CN
3. 3.5
4. CN , H2 O, Cl correct
4. 10.5 correct
5. CN , OH , Cl
5. 7.5
6. H2 CN+ , H4 O2+ , H2 Cl+
Explanation:
Explanation:
044
5.0 points
For gases that do not react chemically with
water, the solubility of the gas in water generally (decreases, increases) with an increase
in the pressure of the gas and (decreases, increases) with increasing temperature.
1. decreases; increases
2. decreases; decreases
Pressure, atm
Version 208 Final rev2 laude (51635)
12
Liquid
Solid
Vapor
3. increases; increases
Temperature, K
4. increases; decreases correct
Explanation:
An increase in pressure means that you
have increased the concentration of gas above
the solvent surface, thereby increasing the
concentration of the gas in the solvent. Increasing the temperature will decrease the
solubility of the gas.
045
5.0 points
Consider the reaction,
The triple point is at 5.1 atm and 217 K.
What happens if CO2 ( ) at 25 atm and 350 K
is released into a room at 1 atm and 298 K?
1. The liquid vaporizes. correct
2. The liquid freezes.
3. The liquid remains stable.
4. The liquid and solid are in equilibrium.
5. The liquid and vapor are in equilibrium.
A(aq ) + B(aq ) C(aq )
The equilibrium constant, K , is 2. If the
concentrations of A, B and C are 2 M, 2 M
and 10 M, respectively, which of the following
would occur?
1. the reaction would move left correct
2. nothing would occur
3. not enough information
4. the reaction would move right
Explanation:
[C]
10
Q=
=
= 2. 5
[A] [B]
22
Since Q > K , the reaction would move
right.
046 5.0 points
The phase diagram for CO2 is given below.
Explanation:
047 5.0 points
What is the average current generated in the
Cu(s) | Cu2+ (aq) || Fe3+(aq) | Fe(s)
electrochemical cell if 50 g of Cu(s) are used
up in a 24 hour period?
Cu2+ + 2 e Cu
E = +0.22 V
red
Fe3+ + 3 e Fe
E = 0.04 V
red
1. 1.76 amp correct
2. 2.64 amp
3. 13.00 amp
4. 111.85 amp
5. 42.17 amp
Explanation:
mCu = 50 g
The half equation of interest is
t = 24 h
Version 208 Final rev2 laude (51635)
Cu(s) Cu2+ (aq) + 2 e
Find the moles of Cu dissolved:
(50 g Cu)
1 mol Cu
= 0.786832 mol Cu
63.546 g Cu
Find the amount of charge carried by the
electrons:
2 mol e
96485 C
(0.786832 mol Cu)
1 mol Cu 1 mol e
= 1.51835 105 C
Find the average current in 24 hours:
[NO(g)]
0.10
0.10
0.10
0.20
0.20
1. propanol (CH3 CH2 CH2 OH)
Rate, M/s
0.0050
0.010
0.015
0.020
0.040
1. None of these
[H2 ]
[NO]
3. rate = k [H2 ]2 [NO]
4. rate = k [H2 ] [NO]2 correct
5. rate = k [H2 ] [NO]
6. rate = k
048 5.0 points
Which of the following alcohols would be the
least miscible with water?
[H2 (g)]
0.10
0.20
0.30
0.10
0.20
What is the rate law for this reaction?
2. rate = k
Colombs = amp second
Coulomb
amp =
second
1.51835 105 C
1h
1 min
=
24 h
60 min
60 s
= 1.75735 C/s = 1.75735 A
13
[H2 ]
[NO]2
Explanation:
050 5.0 points
Which of the following products is not correctly associated with the process name?
2. ethanol (CH3 CH2 OH)
1. nitric acid : Ostwald
3. pentanol (CH3 CH2 CH2 CH2 CH2 OH)
2. elemental sulfur : Claus
4. hexanol (CH3CH2 CH2 CH2 CH2 CH2 OH)
correct
5. methanol (CH3 OH)
Explanation:
The polar OH group is miscible with water but as the nonpolar hydrocarbon chain
lengthens, solubility decreases.
049
For the reaction
5.0 points
2 NO(g) + 2 H2(g) N2 (g) + 2 H2O(g)
the following data were collected.
3. sulfuric acid : Bayer correct
4. ammonia : Haber
5. aluminum metal : Hall
Explanation:
051 5.0 points
What is the pH of 0.25 M KHCO3 (aq)
if Ka1 = 4.3 107 , Ka2 = 5.6 1011 ,
pKa1 = 6.37 and pKa2 = 10.25?
1. 3.02
2. 6.92
Version 208 Final rev2 laude (51635)
14
Explanation:
3. 8.31 correct
O
4. 4.36
5. None of these
6. 7.82
Explanation:
pKa1 = 6.37
pKa2 = 10.25
M = 0.25 M
This is a salt of a polyprotic acid. The salt
will dissociate into solution. The cation is
an extremely weak acid and does not aect
the equilibrium. The anion can then either
protonate or deprotonate; the extent to which
these processes occur is determined by the
relative values of pKa1 and pKa2 . The pH is
1
pH = (pKa1 + pKa2 )
2
1
= (6.37 + 10.25)
2
= 8.31 .
H +
H +
Z1 is true; hydration cannot happen with
any other solvent than water.
Z2 and Z3 are also true since oxygen ( )
will be attracted to the positive Ca+ and
the hydrogen ( +) will be attracted to the
negative Cl ions.
053 5.0 points
When the reaction
3 NO(g) N2 O(g) + NO2 (g)
is proceeding under conditions such that 0.015
mol/L of N2 O is being formed each second,
the rate of the overall reaction is ? and
the rate of change for NO is ? .
1. 0.015 Ms1 ; +0.045 Ms1
2. 0.030 Ms1 ; 0.005 Ms1
Note the pH of a salt solution of a polyprotic
acid is independent of the concentration of
the salt as long as it is not extremely dilute.
3. 0.015 Ms1 ; 0.005 Ms1
052 5.0 points
Consider an aqueous solution of CaCl2 and
the following statements:
Z1) Hydration is a special case of solvation in
which the solvent is water.
Z2) The oxygen ends of water molecules are
attracted toward Ca2+ ions.
Z3) The hydrogen ends of water molecules
are attracted toward Cl ions.
Which response contains all of the statements that are true and no false statements?
5. none of the other answers is correct
1. Z3
2. Z1 and Z2
4. 0.015 Ms1 ; 0.045 Ms1 correct
Explanation:
Notice that three moles of NO are required
to make one mole of N2 O in this reaction,
so the rate of disappearance of NO (which
has a negative sign) is three times the rate of
appearance of N2 O.
054 5.0 points
181 mL of an unknown HCl solution was neutralized in a titration with 36.2 mL of 0.250 M
NaOH. What is the molarity of the unknown
HCl solution?
3. Z1, Z2, and Z3 correct
1. 2.50 101 M
4. Z1
2. 9.05 102 M
5. Z2
3. 1.64 103 M
Version 208 Final rev2 laude (51635)
4. 8.00 101 M
5. 5.00 102 M correct
Explanation:
VHCl = 181 mL
VNaOH = 36.2 mL
[NaOH] = 0.250 M
The balanced equation for this neutralization reaction is
HCl + NaOH NaCl + H2 O
We determine the moles of NaOH used:
? mol NaOH = 0.0362 L soln
0.250 mol NaOH
1 L soln
= 0.00905 mol NaOH
From the 1:1 mole ratio in the balanced chemical reaction we know we would need 0.00905
moles of NaOH to neutralize 0.00905 moles
HCl. This is the amount of HCl that must
have been in the 181 mL sample. Molarity is
moles solute per liter of solution:
0.00905 mol NaOH
0.181 L solution
= 0.05 M HCl
? M HCl =
055 5.0 points
A 0.200 M solution of a weak monoprotic acid
HA is found to have a pH of 3.00 at room
temperature. What is the ionization constant
of this acid?
15
8. 1.0103
Explanation:
056 5.0 points
Which of the equilibrium expressions for
a triprotic acid H3 A would be involved in
the calculation to nd the pH of a solution
found from LiCaA and Na2 HA? Assume the
K values are far apart and Kw is not involved
in the calculation.
1. Ka1
2. Ka1 and Ka2
3. Ka2
4. Ka1 , Ka2 , and Ka3
5. Ka2 and Ka3
6. Ka3 correct
Explanation:
The salts use HA2 and A3 , so Ka3 is
needed.
057 5.0 points
For the chemical reaction taking place in a
battery, the equilibrium constant is always
1. less than 1
2. less than 0
1. 1.8105
3. twice the G
2. 1.0106
4. twice the voltage
5. greater than 1 correct
3. 5.30
4. 5.010
3
5. 2.0105
6. 5.0106 correct
7. 2.0109
Explanation:
The standard cell potential for a battery
is by denition positive. The relationship
n F E = R T ln K , dictates that a positve
value of E will correspond to a value for K
greater than 1.
058
5.0 points
Version 208 Final rev2 laude (51635)
16
A hypothetical reaction
A+2B C+ D
is found to be rst order in A and second order
in B. What are the units of k , the specic rate
constant, if reaction rate is expressed in units
of M/s?
1. 0.65 V
2. 0.48 V
3. 0.55 V correct
4. 0.60 V
1
1. M s
3
2. M
5. 0.72 V
s
3. M2 s1 correct
4. M2 s1
5. M1 s
Explanation:
059 5.0 points
Which of the following statements about the
Clausius Clapeyron equation is not true?
1. As intermolecular forces increase, Hvap
increases and results in a lower boiling point.
correct
2. The functional relationship between vapor pressure and temperature is exponential.
3. With a temperature/vapor pressure data
point and Hvap you can solve for boiling
point.
4. One of the reasons the equation does
yield an exact answer is that it assume gases
are ideal.
Explanation:
When Hvap increases, so does boiling
point - they are directly proportional.
060 5.0 points
What is the cell potential of the following cell?
Pt | Br(aq, 0.2 M) | Br2( ) ||
Au+ (aq, 0.7 M) | Au(s)
Br2 + 2 e 2 Br
Ered = +1.09 V
+
Au + e Au
Ered = +1.69 V
Explanation:
The reaction involving Br must be reversed
(cathode reaction) and the reaction involving
Au must be doubled in order to balance the
electrons:
2 Br (aq) Br2 ( ) + 2 e
Eanode = 1.09 V
2 Au+ (aq) + 2 e 2 Au(s)
Ecathode = +1.69 V
2 Br (aq) + 2 Au+ (aq) Br2 ( ) + 2 Au (s)
Ecell = +0.60 V
To correct for the non-standard concentration we use the Nernst equation:
0.0591
1
log
]2 [Au+ ]2
n
[Br
1
0.0591
log
= 0. 6 V
2
(0.2 M)2 (0.7 M)2
= 0.549536 V.
E = E0